Eating whole grains daily, such as brown rice or whole-wheat bread, reduces colorectal cancer risk, with higher consumption linked to lower risk, according to a new report by the American Institute for Cancer Research (AICR) and the World Cancer Research Fund (WCRF). This is the first time AICR/WCRF research links whole grains independently to lower cancer risk.

"Colorectal cancer is one of the most common cancers, yet this report demonstrates there is a lot people can do to dramatically lower their risk,” said Edward L. Giovannucci, MD, ScD, lead author of the report and professor of nutrition and epidemiology at the Harvard TH Chan School of Public Health. “The findings from this comprehensive report are robust and clear: Diet and lifestyle have a major role in colorectal cancer.”

The new report evaluated the scientific research worldwide on how diet, weight, and physical activity affect colorectal cancer risk. The report analyzed 99 studies, including data on 29 million people, of whom over a quarter of a million were diagnosed with colorectal cancer.

Other factors found to increase colorectal cancer include:

Eating high amounts of red meat (above 500 grams cooked weight a week), such as beef or pork

Being overweight or obese

Consuming two or more daily alcoholic drinks (30 grams of alcohol), such as wine or beer

Lowering Risk with Fiber, Activity, and Grains
The report concluded that eating approximately three servings (90 grams) of whole grains daily reduces the risk of colorectal cancer by 17%.

It adds to previous evidence showing that foods containing fiber decreases the risk of this cancer.

For physical activity, people who are more physically active have a lower risk of colon cancer compared to those who do very little physical activity. Here, the decreased risk was apparent for colon and not rectal cancer.

In the U.S., colorectal cancer is the third most common cancer among both men and women, with an estimated 371 cases diagnosed each day. AICR estimates that 47% of U.S. colorectal cancer cases could be prevented each year through healthy lifestyle changes.

Dr. Giovannucci noted: “Many of the ways to help prevent colorectal cancer are important for overall health. Factors such as maintaining a lean body weight, proper exercise, limiting red and processed meat and eating more whole grains and fiber would lower risk substantially. Moreover, limiting alcohol to at most two drinks per day and avoidance or cessation of smoking also lower risk.”

Fish, Fruits and Vegetables, Emerging Evidence
The report found other links between diet and colorectal cancer that were visible but not as clear. There was limited evidence that risk increases with low intake of both non-starchy vegetables and fruit. A higher risk was observed for intakes of less than 100 grams per day (about a cup) of each.

Links to lowering risk of colorectal cancer was with fish and foods containing vitamin C. Oranges, strawberries and spinach are all foods high in vitamin C.

The research continues to emerge for these factors, but it all points to the power of a plant-based diet, said Alice Bender, MS, RDN, AICR director of nutrition programs. “Replacing some of your refined grains with whole grains and eating mostly plant foods, such as fruits, vegetables, and beans will give you a diet packed with cancer-protective compounds and help you manage your weight, which is so important to lower risk. When it comes to cancer there are no guarantees, but it’s clear now there are choices you can make and steps you can take to lower your risk of colorectal and other cancers.”